An Explicit/Multi-Parametric Controller Design for Pressure Swing Adsorption System
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Pressure swing adsorption (PSA) is a flexible, albeit complex gas separation system. Due to its inherent nonlinear nature and discontinuous operation, the design of a model based PSA controller especially with varying operating conditions, is a challenging task. This work focuses on the design of an explicit/multi-parametric model predictive controller for a PSA system. Based on a system involving four adsorbent beds separating 70 % H2, 30 % CH4 mixture into high purity hydrogen, the key controller objective is to fast track H2 purity to the set point value of 99.99 %. To perform this task, a rigorous and systematic framework is employed. First, a high fidelity PDAE based model is built to mimic the real operation and understand its dynamic behavior. The same model is also used to derive a linear approximate model by applying suitable system identification techniques. Then a model predictive control step is formulated for the reduced model where latest developments in multi-parametric programming are applied to derive a suitable explicit MPC controller. To test the performance of the designed controller and further refine the tuning parameters, closed loop simulations are performed where the PDAE model developed in earlier step act as virtual plant. Comparisons studies of the derived explicit MPC controller are also performed with conventional PID controllers. 2009 IFAC.